Headsets and electrodes for gathering electroencephalographic data

ABSTRACT

Example headsets and electrodes are described herein. Example electrode units described herein include a guide defining an opening and an electrode disposed in the opening. The electrode has a housing, a spring, and a pin. The pin is biased outward from a first end of the housing via the first spring. The example electrode units also include a second spring disposed over the opening adjacent a second end of the housing.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application No. 62/312,953, titled “Headsets and Electrodesfor Gathering Electroencephalographic Data,” filed Mar. 24, 2016. Thisapplication also claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application No. 62/308,193, titled “Headsets and Electrodesfor Gathering Electroencephalographic Data,” filed Mar. 14, 2016. U.S.Provisional Application Nos. 62/312,953 and 62/308,193 are herebyincorporated by this reference in their entireties.

FIELD OF THE DISCLOSURE

This disclosure relates generally to neurological and physiologicalmonitoring and, more particularly, to headsets and electrodes forgathering electroencephalographic data.

BACKGROUND

Electroencephalography (EEG) involves measuring and recording electricalactivity corresponding to neural processes in the brain. EEG data istypically measured using a plurality of electrodes placed on the scalpof a user to measure voltage fluctuations resulting from this electricalactivity within the neurons of the brain.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example headset constructed inaccordance with the teachings of this disclosure for gathering EEGsignals.

FIG. 2 is a plan view of one side (e.g., an inside) of the exampleheadset of FIG. 1.

FIG. 3 is a plan view of another side (e.g., the outside) of the exampleheadset of FIG. 1.

FIG. 4A is a left side view of the example headset of FIG. 1.

FIG. 4B is a right side view of the example headset of FIG. 1.

FIG. 4C illustrates the example headset of FIG. 1 on a head of asubject.

FIG. 4D is a rear view of the example headset of FIG. 1 disposed on arelatively small head.

FIG. 4E is a rear view of the example headset of FIG. 1 disposed on arelatively large head.

FIG. 5 is an exploded view of an example electrode unit having exampleelectrodes that may be used with the example headset of FIG. 1.

FIG. 6 is a partially assembled view of the example electrode unit ofFIG. 5.

FIG. 7 is an assembled view of the example electrode unit of FIG. 5.

FIG. 8 is a side view of the example electrode unit of FIG. 5 with theexample electrodes in an extended position.

FIG. 9 is a side view of the example electrode unit of FIG. 5 with theexample electrodes in a retracted or compressed position.

FIG. 10 is a cross-sectional view of the example electrode unit of FIG.8 taken along line A-A of FIG. 8.

FIG. 11 is a cross-sectional view of the example electrode unit of FIG.9 taken along line B-B of FIG. 9.

FIG. 12 is a perspective view of the example electrode unit of FIG. 5with the example electrodes in an extended position.

FIG. 13 is a perspective view of the example electrode unit of FIG. 5with the example electrodes in a retracted position.

FIG. 14 is a cross-sectional view of the example electrode unit of FIG.12 taken along line C-C of FIG. 12.

FIG. 15 is a cross-sectional view of the example electrode unit of theFIG. 13 taken along line D-D of FIG. 13.

FIG. 16 is a perspective view of another example electrode unit havingan example electrode that may be used with the example headset of FIG.1.

FIG. 17 is a side view of the example electrode unit of FIG. 16.

FIG. 18 is cross-sectional view of the example electrode unit of FIGS.16 and 17 taken along line E-E of FIG. 16.

FIG. 19 is a side view of another example electrode unit having anexample electrode that may be used with the example headset of FIG. 1.

FIG. 20 is another side view of the example electrode unit of FIG. 19.

FIG. 21 is a cross-sectional view of the example electrode unit of FIGS.19 and 20 taken along line F-F of FIG. 20.

FIG. 22 is a perspective view of the example electrode of FIG. 19 in anunassembled state.

FIG. 23 is a top view of the example electrode of FIG. 22.

FIG. 24 is a side view of the example electrode of FIG. 22.

FIG. 25 is a perspective view of the example electrode of FIG. 19 in anassembled state.

FIG. 26 is a top view of the example electrode of FIG. 25.

FIG. 27 is a side view of the example electrode of FIG. 25.

FIG. 28 is a side view of an example housing of the example electrodeunit of FIG. 19.

FIG. 29 is a bottom view of the example housing of FIG. 28.

FIG. 30 is a cross-sectional view of the example housing of FIGS. 28 and29 taken along line G-G of FIG. 28.

FIG. 31 is a side view of the example electrode unit of FIG. 19 showingthe example electrode in a compressed state.

FIG. 32 is another side view of the example electrode unit of FIG. 31.

FIG. 33 is a cross-sectional view of the example electrode unit of FIGS.31 and 32 taken along line H-H of FIG. 32.

FIG. 34 illustrates an example substrate from which multiple ones of theexample electrode of FIG. 19 are stamped during an example manufacturingprocess.

FIG. 35 is an exploded view of another example electrode unit havingexample electrodes that may be used with the example headset of FIG. 1.

FIG. 36 is an assembled view of the example electrode unit of FIG. 35.

FIG. 37 is a side view of the example electrode unit of FIG. 35.

FIG. 38 is another side view of the example electrode unit of FIG. 35.

FIG. 39 is a cross-sectional view of the example electrode unit of FIG.35 taken along line I-I of FIG. 38.

FIG. 40 is an exploded view of an example shielding unit implementedwith the example electrode unit of FIG. 35.

FIG. 41 is a cross-sectional view of an example pogo-pin electrode thatmay be implemented as any of the example electrodes disclosed herein.

Certain examples are shown in the above-identified figures and describedin detail below. In describing these examples, like or identicalreference numbers are used to identify the same or similar elements. Thefigures are not necessarily to scale and certain features and certainviews of the figures may be shown exaggerated in scale or in schematicfor clarity and/or conciseness. Additionally, several examples have beendescribed throughout this specification. Any features from any examplemay be included with, a replacement for, or otherwise combined withother features from other examples.

DETAILED DESCRIPTION

Example headsets disclosed herein may be used to obtain EEG signals froma brain in the head of a subject. Example headsets disclosed hereininclude electrode units that may be removably or permanently coupled tothe headsets. In some examples, an electrode unit is magneticallycouplable to an example headset. In other examples, the electrode unitsare coupled with mechanical fasteners to the headset such as, forexample, a threaded connection or a friction fit. Example electrodeunits include one or more electrodes. In some examples, the electrode(s)include an electrode body and a pin that is retractable into theelectrode body. In some such examples, the pin is biased outward via aspring. In some examples, the electrode(s) include an arm that isbendable or compressible.

Example electrode units disclosed herein include a guide defining anopening and an electrode disposed in the opening. In some such examples,the electrode has a housing, a first spring, and a pin, where the pin isbiased outward from a first end of the housing via the first spring. Insome examples, the electrode unit further includes a second springdisposed over the opening adjacent a second end of the housing.

In some examples, the electrode is a first electrode, the housing is afirst housing and the pin is a first pin. In some such examples, theelectrode unit further includes a second electrode disposed in theopening. In some examples, the second electrode includes a secondhousing, a third spring, and a second pin, where the second pin isbiased outward from a first end of the second housing via the thirdspring. In some examples, the first electrode and the second electrodeare independently adjustable via the first spring and the third spring.In some examples, the first electrode and the second electrode aresimultaneously adjustable via the second spring.

In some examples, the housing is coupled to the second spring. In somesuch examples, the housing includes a protrusion extending through anaperture in the second spring, where the housing is coupled to thesecond spring via staking or press fit. In some examples, the opening isa first opening, and the electrode unit further includes a connectorhaving a second opening. In some such examples, the guide is disposed inthe second opening of the connector. The connector may be coupled to aband to be disposed over a head of a subject. In some examples, theconnector is a magnet. In some examples, the guide is coupled to theconnector via an interference fit. In some examples, the electrode unitfurther includes an electrode unit housing having a third openingdefining a cavity, and the connector is disposed in the third opening.In some examples, the connector is substantially aligned with a bottomof the electrode unit housing, and the guide and the electrode extendfrom the bottom of the electrode unit housing. In some examples, theelectrode is movable through the first opening of the guide into thecavity of the electrode unit housing. In some examples, the secondspring is disposed over the connector and the guide in the secondcavity. In some such examples, when the electrode moves into the cavityof the electrode unit housing, a center of the second spring flexes intothe cavity. In some examples, the electrode unit includes a pusherdisposed in the cavity, and an outer rim of the second spring is coupledbetween the pusher and the connector. In some examples, the pusher isinserted into the cavity from a fourth opening in the electrode unithousing opposite the third opening. In some examples, the electrode unithousing includes a ledge in the opening, wherein an outer rim of thesecond spring is coupled between the connector and the ledge. In someexamples, an outer rim of the second spring remains in contact with theconnector when the center of the second spring flexes into the cavity.In some examples, the second spring is a spiral spring plate.

Example electrode units disclosed herein include a housing defining acavity, conductive paste disposed on an inner wall of the cavity and anelectrode disposed in the cavity and spaced apart from the inner wall ofthe cavity. In some such examples, the electrode extends from thecavity, and the conductive paste is to shield the electrode from noise.In some examples, the electrode unit includes a layer of insulationdisposed between the electrode and the housing.

Example headsets disclosed herein include the disclosed electrode unitand a band to be disposed over a head of a subject. In some suchexamples, the band has an aperture extending through the band. In someexamples, the electrode unit is to be coupled to the band and extendthrough the aperture. In some examples, the headset includes a pincoupled to the band adjacent the aperture, and the pin is to engage abottom of the housing. In some examples, the conductive paste is furtherdisposed on the bottom of the housing. In some examples, the pin iselectrically coupled to a shielding electrode to be placed on the headof the subject. In some such examples, the pin is electrically coupledto the shielding electrode via a printed circuit board disposed in theband. In some examples, the headset further includes a head band, andthe shielding electrode is coupled to the head band to contact aforehead of the subject. In some examples, the electrode unit includes afirst connector and the band includes a second connector, where thefirst connector may be removably coupled to the second connector. Insome examples, the first connector is a magnet and the second connectoris a metal. In some examples, the second connector is a metal ringdisposed around the aperture.

Example shielding units are disclosed herein. An example shielding unitincludes a bottom cover having an opening extending from a top side to abottom side of the bottom cover. The example shielding unit alsoincludes a top cover coupled to the top side of the bottom cover.Conductive paste is disposed on a bottom of the top cover. The exampleelectrode unit further includes a pin disposed in a channel extendingthrough the bottom cover, where the pin is in contact with theconductive paste on the top cover and extends from the bottom side ofthe bottom cover.

In some examples, the pin is a pogo-pin. In some such examples, theshielding unit further includes an electrode unit and the electrode unitis disposed in the opening in the bottom cover. In some examples, theelectrode unit is coupled to the bottom cover via an interference fit.In some examples, the electrode unit includes an electrode extendingfrom the bottom side of the bottom cover.

Example headsets disclosed herein include the disclosed shielding unitand a band to be disposed over a head of a subject. The band has anaperture extending through the band, and the shielding unit is coupledto the band and the electrode extends through the aperture. In someexamples, the band includes an electrical pad adjacent the aperture,where the pin engages the electrical pad. In some examples, theelectrical pad is electrically coupled to a shielding electrode to beplaced on the head of the subject. In some examples, the pin iselectrically coupled to the shielding electrode via printed circuitboard disposed in the band.

Some example electrode units disclosed herein include a housing having acavity defined by an opening in a side of the housing and an electrode.In some such examples, the electrode includes a ring disposed in theopening and an arm, where the arm has a first portion extending outwardfrom the opening away from the housing and a second portion extendingfrom an end of the first portion toward the housing and into the cavity,and the first and second portions connect at a bend.

In some examples, the first portion of the arm extends through the ringand outward from the opening away from the housing. In some suchexamples, the second portion of the arm extends through the ring andinto the cavity. In some examples, the cavity includes a channelextending into the housing. In some such examples, the second portion ofthe arm is movable into the channel when a force is applied to the bend.

In some examples, the electrode unit includes a connector coupled to thehousing around the opening to couple the housing to a band to be wornover a head of a subject. In some examples, the ring is coupled betweenthe connector and the housing. In some such examples, the connector is amagnet. In some examples, the housing includes a guide, and the guide isto extend through the ring of the electrode to align the electrode inthe housing. In some examples, the first portion is to move toward thesecond portion when a force is applied to the bend. In some examples,the ring and the arm are integral.

Example headsets disclosed herein include the disclosed electrode unitand a band to be disposed over a head of a subject. The band includes anaperture extending through the band, and the electrode unit is coupledto the band and the first portion of the arm extends through theaperture.

In some examples, the electrode unit includes a first connector and theband includes a second connector, where the first connector is removablycoupled to the second connector. In some examples, the first connectoris a magnet and the second connector is a metal. In some examples, thesecond connector is a metal ring disposed around the aperture.

Turning now to the examples illustrated in the figures, FIG. 1 shows anexample headset 100 for gathering EEG signals from the head of a subject(e.g., a person). As used herein, a subject may be any person, user,viewer, participant and/or panelist. A panelist may be, for example, auser registered on a panel maintained by a ratings entity (e.g., anaudience measurement company) that owns and/or operates a ratings entitysubsystem. Traditionally, audience measurement entities (also referredto herein as “ratings entities”) determine demographic reach foradvertising and media programming based on registered panel members.That is, an audience measurement entity enrolls people that consent tobeing monitored into a panel. During enrollment, the audiencemeasurement entity receives demographic information from the enrollingpeople so that subsequent correlations may be made betweenadvertisement/media exposure to those panelists and differentdemographic markets. People become panelists via, for example, a userinterface presented on the media device (e.g., via a website). Peoplebecome panelists in additional or alternative manners such as, forexample, via a telephone interview, by completing an online survey, etc.Additionally or alternatively, people may be contacted and/or enlistedusing any desired methodology (e.g., random selection, statisticalselection, phone solicitations, Internet advertisements, surveys,advertisements in shopping malls, product packaging, etc.).

In the illustrated example, the headset 100 includes a body having bandsthat are shaped to extend over a head of a subject. The body 102includes a head band 104 that fits over the head of the subject. In theillustrated example, the head band 104 is a continuous ring. In theillustrated example, the body 102 includes a first band 106, a secondband 108 and a third band 110 that are positioned to extend over thehead of subject from the left to the right sides of the head. In theillustrated example, the first, second and third bands 106, 108, 110 arecoupled to the head band 104 by a midline band 112. The midline band 112extends from the head band 104 and is positioned to extend over the headof the subject from the front to the rear of the head, or from the backto the front of the head (e.g., along the midline), depending on theorientation the headset 100 is worn. In other examples, the headset 100may be worn in other orientations (e.g., the front of the headset 100may be positioned on the rear of the head). In some examples, theheadset may include more or fewer bands. The number of bands, lengths ofbands, shapes of bands, orientation of bands, etc. may be based on thedesired number of channels from which EEG signals are to be gatheredand/or the desired locations of measurement.

In some examples, electrodes are coupled to the body 102 of the headset.In some examples, electrodes are coupled to each of the head band 104,the first band 106, the second band 108, the third band 110 and themidline band 112. In other examples, only certain ones of the head band104, the first band 106, the second band 108, the third band 110 and/orthe midline band 112 include electrodes. The electrodes may be coupledto apertures formed in the body 102, as disclosed in further detailherein.

In the illustrated example of FIG. 1, the head band 104 forms acontinuous ring. In other examples, the head band 104 may be divided orsplit, and two ends of the head band 104 may be coupled together. Insome examples, the body 102 is a substantially unitary part or component(e.g., a monolithic structure formed in one piece in a mold). In otherexamples, the body 102 may be constructed of multiple parts orcomponents that are coupled (e.g., fastened) together. In some examples,the body 102 of the headset 100 is silicone, rubber or plastic. In suchexamples, the body 102 is relatively flexible yet retains its generalshape.

In some examples, the headset 100 includes apertures to receiveelectrodes. FIG. 2 shows a bottom, inside view of the body 102 of theexample headset 100 in a flattened positioned, and FIG. 3 shows a top,outside view of the body 102 of the example headset 100 in a flattenedposition. In the illustrated example of FIGS. 2 and 3, the headset 100includes a first aperture 200 a (e.g., an opening, a hole, etc.) formedin the body 102 to receive an electrode. For example, an electrode(e.g., such as the electrode unit 500 of FIG. 5, disclosed in furtherdetail here) may be coupled to the first aperture 200 a. In someexamples, the headset 100 includes a plurality of apertures for aplurality of electrodes, such as apertures 200 b-200 n. Any number (n)of apertures may be employed. The apertures 200 a-200 n may be formed inany of the head band 104, the first band 106, the second band 108, thethird band 110 and/or the midline band 112.

To connect an electrode to the first aperture 200 a, a first connector202 a is disposed adjacent the first aperture 200 a, as illustrated inthe example of FIG. 3. In some examples, the first connector 202 a is ametal ring, and an electrode (or electrode unit) may include a magnet tocouple the electrode (or electrode unit) to the first connector 202 a.In other examples, the first connector 202 a is magnetic. In otherexamples, other types of connectors (e.g., mechanical connectors) may beimplemented. In the illustrated example, the first connector 202 aencompasses or surrounds the first aperture 200 a. In some examples, aplurality of connectors is used, and each of the connectors isassociated with a respective one of the plurality of apertures 200 a-200n. For example, a plurality of connectors 202 a-202 n is illustrated inFIG. 3 for the plurality of apertures 200 a-200 n. Although theillustrated example associates a connector with each aperture, fewerconnectors than apertures may alternatively be used.

In some examples, the headset 100 includes a printed circuit board (PCB)(e.g., a substrate on which circuitry may be mounted and/or printed)disposed within the body 102. For example, silicone or another materialmay be molded around a PCB to form the body 102 of the headset 100. ThePCB may be flexible and may include traces or wires to form circuitry.In some examples, the connectors 202 a-202 n (e.g., the wires or tracesof the PCB) are in circuit with one or more of the apertures 200 a-200 nand/or an electrical connector 300 (FIG. 3), discussed in further detailherein. In some examples, the PCB is formed of one board. In otherexamples, the PCB may be constructed of multiple sections or portionsand/or multiple PCBs may be employed. For example, as illustrated inFIG. 3, the headset 100 may include a first PCB 301 in a first part 302of the head band 104, a second PCB 303 in a second part 304 of the headband 104 and a third PCB 305 in a third part 306 of the headset 100. Inthe illustrated example, the third part 306 includes a portion of thehead band 104, the first band 106, the second band 108, the third band110 and the midline band 112. The PCBs 301, 303, 305 may be in circuit(e.g., in electrical and/or magnetic connection) to form an overallcircuit (or compound PCB) extending throughout the body 102 of theheadset 100. In some examples, when multiple PCBs are used, relativelysmaller PCBs or PCB sections can be cut from one piece of PCB materialto thereby reduce waste compared to cutting the entire headset PCB inone piece. In other words, when cutting relatively smaller PCBs or PCBsections, the templates can be arranged closer together to minimizewaste between adjacent pieces. In addition, in some examples, employingmultiple PCBs results in increased adjustability and movement betweensections of the head band 104, and avoids large areas of rigidity, whichmight be exhibited by a large PCB. Thus, employing multiple PCBs 301,303, 305 increases comfort for the wearer of the headset 100.

In some examples, the headset 100 may include one or more tension strapsto tighten the headset 100 on the head of a subject. For example, FIG.4A is a left side view of the example headset 100. A first tension strap400 (e.g., a cord) is coupled to one end of the first band 106, a secondtension strap 402 is coupled to one end of the second band 108, and athird tension strap 404 is coupled to one end of the third band 110. Insome examples, the first, second and third tension straps 400, 402, 404are elastic (e.g., rubber and/or silicone). The first, second and thirdtension straps 400, 402, 404 are coupled to a cover 406 (e.g., aconnector). In the illustrated example, a pull strap 408 is coupledbetween the cover 406 and a first connector 410. The first connector 410may be pulled to tighten the first, second and third tension straps 400,402, 404 and, thus, to tighten the first, second and third bands 106,108, 110 over the head of a subject. In the illustrated example, thecover 406 operates as connector or joiner where the straps 400, 402,404, 408 are coupled. In other examples, the straps 400, 402, 404, 408are coupled to each other and the cover 406 covers the connection. Thefirst connector 410 couples to another connector extending from theright side of the headset 100 (disclosed in further detail herein).Therefore, the first, second and/or third bands 106, 108, 110 may betightened or loosened together (e.g., simultaneously) by, for example,pulling or relaxing the pull strap 408. Additionally or alternatively,the first, second and/or third bands 106, 108, 110 may be independentlyadjusted. For example, as illustrated in FIG. 4A, the first tensionstrap 400 extends through a first opening 401 in the first band 106(e.g., adjacent the end of the first band 106). The first opening 401 isdimensioned to create friction between the first band 106 and the firsttension strap 400. The friction force is sufficient to couple the firsttension strap 400 to the first band 106 when pulling the cover 406, forexample. To shorten the effective length of the first tension strap 400(e.g., the length of the first tension strap 400 between the end of thefirst band 106 and the cover 406), the end of the first tension strap400 may be pulled (with sufficient force to overcome the friction) toslide the first tension strap 400 through the first opening 401. Tolengthen or loosen the effective length of the first tension strap 400,the first tension strap 400 can be pulled from the opposite side of thefirst band 106. In some examples, teeth are provided in the firstopening 401. An example assembly and cross-sectionals views are shows inthe enlarged portion of FIG. 4A. In the illustrated example, an end cap407 is coupled to the end of the first band 16. The end cap includes apassage 409 having teeth 411. The teeth 411 are angled to createfriction against the first tension strap 400 when pulling the firsttension strap 400 toward the head band 104 to loosen the first tensionstrap 400. Similar to the first opening 401, the second band 108includes a second opening 403 through which the second tension strap 402extends, and the third band 110 includes a third opening 405 throughwhich the third tension strap 404 extends. Therefore, the first, secondand third tensions straps 400, 402, 404 may be adjusted independently ofeach other.

In some examples, the head band 104 includes one or more passageways forthe first, second and/or third tension straps 400, 402, 404. Forexample, as illustrated in FIG. 4A, a first passageway 412 (e.g., achannel, a through-hole, etc.) is provided in the head band 104. Thefirst tension strap 400 extends through the first passageway 412. In theillustrated example, a second passageway 414 and a third passageway 416are similarly provided for the second and third tension straps 402, 404.In some examples, two or more of the first, second and/or third tensionstraps 400, 402, 404 extend through the same passageway.

FIG. 4B is a right side view of the example headset 100. Similar to theleft side (see FIG. 4A), the right side includes a fourth tension strap418 (e.g., a cord), which may be coupled to the other end of the firstband 106 opposite the first tension strap 400 (FIG. 4A), a fifth tensionstrap 420 coupled to the other end of the second band 108 opposite thesecond tension strap 402 (FIG. 4A), and a sixth tensions strap 422coupled to the other end of the third band 110 opposite the thirdtension strap 404 (FIG. 4A). The fourth, fifth and sixth tension straps418, 420, 422 are coupled to a second cover 424. Similar to thepassageways 412, 414, 416 (FIG. 4A), the headset 100 includes one ormore passageways for the fourth, fifth and/or sixth tension straps 418,420, 422. In the illustrated example, a pull strap 426 is coupledbetween the second cover 424 and a second connector 428. In theillustrated example, the cover 406 operates as connector or joiner wherethe straps 418, 420, 422, 426 are coupled. The second connector 428 maybe pulled to tighten the fourth, fifth and sixth tension straps 418,420, 422 and, thus, to tighten the first, second and third bands 106,108, 110 over the head of a subject. Also, similar to the first, secondand third tension straps 400, 402, 404, the fourth, fifth and sixthtension straps 418, 420, 422 are independently adjustable by sliding thetension straps 418, 420, 422 through the respective openings to increaseor decrease the effective length of the respective straps 418, 420, 422.

In some examples, the first connector 410 (FIG. 4A) and the secondconnector 428 (FIG. 4B) may be pulled taut and coupled to each other(e.g., beneath the chin of the wearer, behind the head of the wearer,etc.) to retain the headset 100 to a head of a subject. For example,FIG. 4C illustrates the example headset 100 on a head 430 of a subject.The first connector 410 is coupled to the second connector 428 at a rearof the head 430. In the illustrated example, the first connector 410 isimplemented as a loop and the second connector 428 is implemented as ahook. In other examples, the first and second connectors 410, 428 may beother types of connectors, such as a button, a snap, a magnet, Velcro®,and/or any other suitable fastener. In other examples, the first andsecond connectors 410, 428 are connected under a chin of the subject.

In the illustrated example of FIGS. 4A-4C, the headset 100 includes theelectrical connector 300 to which a processor (e.g., a controller, amicroprocessor, a central processing unit (CPU), an application-specificintegrated circuit (ASIC) or the like) can be connected. As disclosedabove, the headset 100 may include one or more PCBs disposed within thebody 102 (e.g., integrated within the body 102). The PCB(s) includetraces or wires that communicatively couple one or more electrode(s)positioned in respective ones of the apertures 200 a-200 n to theelectrical connector 300. As such, signals gathered by the electrodesare transmitted to the processor for collection and/or analysis. Anexample processor 434 is illustrated in FIG. 4C. The example processor434 includes an electrical connector 436 that can be plugged into theelectrical connector 300. In some examples, the processor 434 conditionsthe signals, filters/attenuates noise, provides additional signalprocessing and/or signal analysis and/or outputs data to an externaldevice. In some examples, the processor 434 includes a transmitter totransmit signals gathered by the electrodes and/or data based on suchsignals.

In the illustrated example of FIGS. 4A-4C, the two ends of the head band104 are coupled together via a latch or lock 438. As illustrated inFIGS. 2 and 3, the head band 104 is divided into the first part 302 andthe second part 304, which extend from the midline band 112. The firstpart 302 is shorter than the second part 304. As such, the lock 438connecting the ends of the first and second parts 302, 304 is offsetfrom a rear of the head 430 of the subject (e.g., not position in themiddle of the back of the head 430). Therefore, one or more electrodescan be positioned on the rear section of the head band 104 along therear of the head 430, which is beneficial to gather EEG signals that aregenerated along the midline of the head near the rear or inion. Forexample, FIG. 4D shows a rear view of the headset 100 on a relativelysmall head. In the illustrated example, the back of the head band 104includes four apertures (and connectors) where electrodes can beconnected (and gather signals). In particular, the head band 104includes the first aperture 200 a, the second aperture 200 b, the thirdaperture 200 c and a fourth aperture 200 d. In the illustrated example,the third aperture 200 c is located along (or near) the midline of thehead 430. Thus, in this instance, the third aperture 200 c may be usedwith an electrode to gather signals from the midline of the head 430.The second aperture 200 b, which is to the left of the midline, and thefourth aperture 200 d, which is to the right of the midline, may be usedwith electrodes to gather signals to the immediate left and right,respectively, of the midline. Therefore, the midline, the left midlineand the right midline locations may be accessed by electrodes. In someexamples, the first aperture 200 a may be left empty (no electrodeinserted) or not activated.

When the headset 100 is used by a subject with a larger head, the rearof the head band 104 is disposed in a different location. For example,FIG. 4E shows the headset 100 on a larger head. As illustrated, thesecond aperture 200 b is disposed along the midline of the head 430.Thus, in this configuration, the second aperture 200 b may be used withan electrode to gather signals from the midline, and the first aperture200 a and the third aperture 200 c may be used to gather left and rightmidline signals, respectively. Therefore, the example headset 100 can beused to obtain signals from the same three locations (a midline, a leftand a right) when used on different sized heads.

In the illustrated example of FIGS. 4A-4E, supports 440 a-440 n areprovided around the respective apertures 200 a-200 n. The supports 440a-440 n provide support and centering for the electrodes that may beattached to and extend through the respective apertures 200 a-200 n. Forexample, as illustrated in FIG. 4D, a first support 440 a is providedaround first aperture 200 a, a second support 440 b is provided aroundthe second aperture 200 b, etc. In some examples, the supports 440 a-440n are constructed of plastic.

To adjust the head band 104, the example headset 100 includes the lock438. As illustrated in FIG. 4D, the lock 438 includes a release tab 442that moves between a locked position and an unlocked position. In theillustrated example, the release tab 442 is in the locked position (tothe left in FIG. 4D). The example headset 100 includes a first top wire444 a and a first lower wire 444 b. As illustrated in FIGS. 4A and 4C,the first top and bottom wires 444 a, 444 b extend along the left sideof the headset 100. The first top and bottom wires 444 a, 444 b arecoupled to a fifth support 440 e of a fifth electrode aperture 200 e onthe left side of the head band 104. The first top and bottom wires 444a, 444 b extend rearward and pass through respective channels in a sixthsupport 440 f and a seventh support 440 g. Example channels areillustrated on the sixth support 440 f in FIG. 4A (shown in dashedlines). Referring back to FIG. 4D, the first top and bottom wires 444 a,444 b extend through channels in the first support 440 a, throughchannels in the release tab 442, and through channels in the secondsupport 440 b. The first top and bottom wires 444 a, 444 b are coupledto a pull tab 446. The channels in the release tab 442 are offset fromthe channels in the first support 440 a. As a result, when the releasetab 442 is in the lock position (to the left and adjacent the firstsupport 440 a), the path for the first top and bottom wires 444 a, 444 bcreates friction that prevents the first support 440 a from slidingalong the first top and bottom wires 444 a, 444 b. This is shown in theencircled area of FIG. 4D, which is an enlarged partial cross-sectionalview of the first support 440 a, the release tab 442 and the secondsupport 440 b showing example channels. In the illustrated example, thefirst support 440 a includes a first channel 441 and the release tab 442includes a second channel 443. The first channel 441 is slanted orangled with respect to the second channel 443, such that the first andsecond channels 441, 443 are not aligned when the first support 440 aand the release tab 442 are adjacent each other. When the release tab442 is in the locked position (to the left), the first top wire 444 a isforced to bend through the channels 441, 443, which creates friction,thereby preventing the first support 440 a from sliding along the firsttop wire 444 a. Thus, the ends of the head band 104 are locked in placerelative to each other. To release or adjust the head band 104, therelease tab 442 is moved to the right (towards the second support 440b), which reduces or eliminates the friction. As a result, the first topand bottom wires 444 a, 444 b can slide freely through the first andsecond supports 440 a, 400 b and the release tab 442. The pull tab 446can be pulled to the right to move the ends (the parts 302, 304 of FIG.3) of the head band 104 toward each other, or can be moved back to theleft to release the tensions and allow more space between the ends ofthe head band 104, as illustrated in FIG. 4E. The first top and bottomwires 444 a, 444 b increase the structural integrity of the head band104. In some examples, the head band 104 is constructed of rubber (oranother flexible material) and may tend to bend away from the head 430.In such an instance, the first top and bottom wires 444 a, 444 b hold orsupport the head band 104 in place. In some examples, the first top andbottom wires 444 a, 444 b are steel wires. In some examples, more thantwo wires may be implemented. In other examples, only one wire may beimplemented instead of two. In some examples, the wire(s) may be coupledto other ones of the supports 440 a-440 n and/or to other locations onthe head band 104. As illustrated in FIG. 4D, a spacer 448 is providedsupport the extra length of the first top and bottom wires 444 a, 444 b.The spacer 448 is movable along the head band 104. For example, asillustrated in FIG. 4E, the spacer 448 is moved further to the right.

As illustrated in FIG. 4B, the headset 100 includes a second top wire450 a and a second bottom wire 450 b, which extend along the right sideof the headset 100. The second top and bottom wires 450 a, 450 b arecoupled to an eighth support 440 h and extend rearward through channelsin a ninth support 440 i, a tenth support 440 j, etc. Referring back toFIG. 4D, the second top and bottom wires 450 a, 450 b extend channels inthe supports along the back of the head 440 and are coupled to thesecond support 440 b. In some examples, the second top and bottom wires450 a, 450 b also provide structural integrity to the head band 104. Insome examples, more than two wires may be implemented. In some examples,the second top and bottom wires 450 a, 450 b are steel wires. In someexamples, the wire(s) may be coupled to other ones of the supports 440a-440 n and/or to other locations on the head band 104. In otherexamples, other tightening mechanisms and/or lock mechanisms may beimplemented on the headset 100. In other examples, the head band 104 maybe split or divided differently to dispose the lock 438 in otherlocations on the head 430 to ensure electrodes may be placed on areasdesirable for EEG signal collection. In some examples, a processorsupport 452 (FIGS. 4D and 4E) is coupled to the headset 100 to support aprocessor (e.g., the processor 434 of FIG. 4C) when attached to theheadset 100.

FIG. 5 shows an example electrode unit 500 that may be used with theexample headset 100 of FIGS. 1-4E or another headset. The electrode unit500 may be coupled to the first aperture 200 a of FIGS. 2 and 3, forexample. In some examples, multiple ones of the electrode unit 500 areused with the example headset 100 of FIGS. 1-4E.

In the illustrated example, the electrode unit 500 includes a pusher502, a spring 504, a connector 506, a guide 508, a first electrode 510,a second electrode 512 and a housing 514. The guide 508 defines anopening 516. In the illustrated example, the first and second electrodes510, 512 are slidably disposed within the opening 516 (e.g., a passage,a through-hole). The guide 508 is dimensioned to be disposed within anopening 518 in the connector 506. In some examples, the guide 508 iscoupled to the connector 506 via an interference fit (e.g., friction orpress fit). Additionally or alternatively, in some examples a chemicalfastener such as an adhesive and/or a mechanical fastener(s) may be usedto couple the guide 508 to the connector 506. In the illustratedexample, the connector 506 is ring-shaped. The spring 504 is dimensionedto be disposed over the connector 506 and the guide 508. In theillustrated example, the spring 504 is a spiral spring plate. In anunbiased or relaxed position, the spring 504 is substantially flat orplanar, as shown in the position in FIG. 5.

In the illustrated example, the guide 508 (with the first and secondelectrodes 510, 512), the connector 506 and the spring 504 aredimensioned to be disposed in a cavity 520 of the housing 514, such thatthe first and second electrodes 510, 512 extend from a bottom 522 of thehousing 514. In the illustrated example, a first opening 521 in thehousing 514 and a second opening 523 in the opposite side of the housing514 define the cavity 520. The second spring 504 is disposed over theconnector 506 and the guide 508 in the cavity 520. In some examples, theconnector 506 is coupled to the housing 514 via an interference fit(e.g., friction or press fit). Additionally or alternatively, in someexamples a chemical fastener such as an adhesive and/or a mechanicalfastener(s) may be used to couple the connector 506 to the housing 514.

In the illustrated example, the electrodes 510, 512 are implemented aspins. However, in other examples, the electrodes may have other desiredshapes such as, for example, rings, balls, hook-shaped, etc.

In the example of FIG. 6, the spring 504, the connector 506 (FIG. 5) andthe guide 508 (FIG. 5) (with the first and second electrodes 510, 512)are disposed within the housing 514. As illustrated in FIGS. 5 and 6,the pusher 502 of this example includes a top 524 and a wall 526extending from the top 524. As illustrated in FIG. 7, the pusher 502 ofthis example may be inserted into the cavity 520 (FIG. 5) of the housing514 (through the second opening 523 (FIG. 5) of the housing 514). Inparticular, the wall 526 (FIGS. 5 and 6) is received within the cavity520 (FIG. 5). The top 524 (FIGS. 5 and 6) includes a lip 527, the bottomsurface of which engages a top 528 (FIG. 5) of the housing 514. In someexamples, the pusher 502 is coupled to the housing 514 via aninterference fit (e.g., friction or press fit). Additionally oralternatively, in some examples a chemical fastener such as an adhesiveand/or a mechanical fastener(s) may be used to couple the pusher 502 tothe housing 514.

FIG. 8 is a side view of the example electrode unit 500 with the firstand second electrodes 510, 512 (FIG. 5) in the extended position, andFIG. 9 is a side view of the example electrode unit 500 with the firstand second electrodes 510, 512 (FIG. 5) in the retracted position. FIG.10 is a cross-sectional view of the electrode unit 500 of FIG. 8 takenalong line A-A of FIG. 8, and FIG. 11 is a cross-sectional view of theelectrode unit 500 of FIG. 11 taken along line B-B of FIG. 9. Asillustrated in FIGS. 8-11, the guide 508 is received within theconnector 506, and the connector 506 is received within the cavity 520of the housing 514. The connector 506 is substantially aligned with thebottom 522 (FIGS. 10 and 11) of the housing 514, and the guide 508 andthe first and second electrodes 510, 512 extend from the bottom 522 ofthe housing 514.

As shown in the illustrated example of FIGS. 10 and 11, the firstelectrode 510 includes a first electrode body 1000 (e.g., a housing, asheath) and a first pin 1002 (e.g., a pogo pin). The first electrodebody 1000 receives the first pin 1002 within a first cavity 1004 of thefirst electrode body 1000. The first pin 1002 of the illustrated exampleis retractable into the first cavity 1004 and biased outward from thefirst electrode body 1000 (e.g., from an end of the first electrode body1000) by a first spring 1006 that is disposed within the first cavity1004. A tip 1008 of the first pin 1002 contacts the scalp of the head ofa subject and senses the EEG signals. The first spring 1006 allows thefirst pin 1002 to retract into the first electrode body 1000 when forceis applied downward against the scalp and, thus, increases the comfortand wearability of the headset (e.g., the headset 100 of FIG. 1) byreducing the pressure the first electrode 510 applies to the scalp. Insome examples, to prevent the first pin 1002 from being inadvertentlyremoved from the first electrode body 1000, the first pin 1002 iscoupled (e.g., via welding) to one end of the first spring 1006, and theother end of the first spring 1006 is coupled to the first electrodebody 1000. Additionally or alternatively, the first pin 1002 may includea leg or lip that abuts a rim around the inside of the first cavity1004. The leg or lip may be forced passed the rim (e.g., via a snap fit)when first inserting the first pin 1002 into the first cavity 1004. Inother examples, a chemical fastener such as an adhesive and/or amechanical fastener(s) may be used prevent the first pin 1002 from beingcompletely ejected from the first electrode body 1000. Different sizesprings or springs of different material may be utilized with the firstelectrode 510 to provide more or less biasing force. In some examples,the first spring 1006 provides around 0.2 Newtons of force. In theillustrated example, the first spring 1006 is a coil spring. In otherexamples, the first spring 1006 may be implemented by any other type ofspring such as, for example, a leaf spring.

In the illustrated example of FIGS. 10 and 11, the second electrode 512is substantially the same as (e.g., identical to) the first electrode510. In particular, the second electrode 512 includes a second electrodebody 1000, a second pin 1002, a second cavity 1004, a second spring 1006and a second tip 1008. As such, the second electrode 512 operatessubstantially the same as the first electrode 510. Thus, to reduceredundancy, the second electrode 512 will not be further describedherein. Instead, the interested reader is referred to the disclosureabove relating to the first electrode 510 for a complete description ofthe second electrode 512.

In the extended position of the pins 1002 illustrated in FIGS. 8 and 10,the spring 504 (FIG. 10) is substantially flat, and the ends of thefirst electrode body 1000 of the first electrode 510 and the secondelectrode body 1000 of the second electrode 512 are disposed flush withthe opening 516 of the guide 508 (see FIG. 10). In addition, the firstpin 1002 of the first electrode 510 extends from the first cavity 1004(e.g., from a first end) of the first electrode body 1000, and thesecond pin 1002 of the second electrode 512 extends from the secondcavity 1004 of the second electrode body 1000. A first top 1010 (e.g., asecond end) of the first electrode body 1000 engages the spring 504, anda second top 1010 of the second electrode body 1000 engages the spring504. The second spring 504 is disposed over the opening 516 adjacent thefirst top 1010 and the second top 1010 of the first and secondelectrodes 510, 512. In some examples, the first top 1010 and/or thesecond top 1010 are coupled to the spring 504. In the illustratedexample, the outer rim/perimeter of the spring 504 is coupled (e.g.,retained) between the wall 526 of the pusher 502 and the connector 506,which are coupled to the housing 514 (e.g., via an interference fit). Insome examples, the pusher 502 provides force to keep the spring 504 incontact with the connector 506 (e.g., for communicating EEG signalstherethrough). In some examples, the pusher 502 covers the internalcomponents of the electrode unit 500 to prevent accidently damage and/orcontact with the spring 504.

In some examples, the first electrode 510 is coupled (e.g., fixedlycoupled) to the spring 504 via staking or press fit. For example, thefirst electrode 510 includes a first protrusion 530 (e.g., a boss) (asshown in FIGS. 5 and 10) extending from the first top 1010 of the firstelectrode body 1000. As illustrated in FIG. 5, the spring 504 includes afirst aperture 532 (e.g., a hole). The first protrusion 530 is insertedinto the first aperture 532 and flattened or deformed (e.g., via astaking punch, or heat) to fasten the first electrode 510 to the spring504. Similarly, the second electrode 512 includes a second protrusion530 (e.g., a boss) (as shown in FIGS. 5 and 10) extending from thesecond top 1010 of the second electrode body 1000, and the spring 504includes a second aperture 536 through which the second protrusion 530can be inserted and fastened (e.g., via deformation). Additionally oralternatively, in some examples other mechanical and/or chemicalfastener(s) may be used to couple the first electrode 510 and/or thesecond electrode 512 to the spring 504. For example, the first electrode510 and/or the second electrode 512 may be soldered to the spring 504.In the illustrated example, the first electrode 510 and the secondelectrode 512 are independently adjustable via the respective thesprings 1006.

In the retracted position of the electrode pins 1002 illustrated inFIGS. 9 and 11, the first and second electrodes 510, 512 have beenforced through the opening 516 in the guide 508 and into the spring 504such that the tops 1010 are disposed above the opening 516 and furtherwithin the guide 508 (see FIG. 11). In other words, the first and secondelectrodes 510, 512 are movable through the opening 516 of the guide 508into the cavity 520 of the housing 514. The spring 504 flexes to enablethis movement of the first and second electrodes 510, 512 to theretracted position. In particular, when the first and second electrodes510, 512 move into the cavity 520 of the housing 514, a center of thespring 504 flexes into the cavity 520. As the center of the spring 504flexes, the outer rim of the spring 504 remains in contact with theconnector 506. The spring 504, thus, further softens the force of thepins 1002 against the scalp and increases comfort to the subject wearingthe headset 100 because the spring 504 enables the first and secondelectrodes 510, 512 to retract into the housing 514 and the pusher 502when a sufficient force is applied by, for example, a tightening of theheadset 100. By comparing FIGS. 10 and 11, it can be seen that, inaddition to the extension of the spring 504, the springs 1006 within theindividual electrodes 510, 512 compress when subjected to force. Thus,the spring 504 and the springs 1006 provide an additive force on thescalp. The springs 1006 in the electrodes 510, 512 enable the electrodepins 1002 to independently adjust to bumps and curves on the scalp.Thus, the first pin 1002 has been retracted into the first electrodebody 1000 and the second pin 1002 has been retracted into the secondelectrode body 1000, which further softens the force against the scalpand increases comfort. Without the spring 504, retraction of theelectrode pins 1002 would be limited by the first electrode body 1000and second electrode body 1000, respectively, and any additionalapplication of force would be transmitted from the first pin 1002 andsecond pin 1002 into the scalp of the subject wearing the headset 100.Because the first electrode body 1000 and the second electrode body 1000are independently movable, depending on the placement of the electrodes,the curvature of the scalp, an amount of hair, and/or a degree to whichthe bands are tightened or loosened, the first electrode body 1000 mayextend a first distance from the guide 508, and the second electrodebody 1000 may extend a second distance from the guide 508. In someexamples, the second distance is different than the first. In someexamples, the first electrode 510 and second electrode 512 aresimultaneously adjustable via the spring 504 and independently adjustedvia the springs 1006.

In the illustrated example, the connector 506 is magnetic. As such, theelectrode unit 500 may be magnetically coupled to the body 102. Forexample, the first connector 202 a of FIG. 3 is a magnetic ring and theconnector 506 (FIGS. 5, 10 and 11) is a magnetic ring. Thus, forexample, when the electrode unit 500 is placed on the first aperture 200a, the first connector 202 a and the connector 506 magnetically couplethe electrode unit 500 to the body 102. In the illustrated example,bottom of the guide 508 extends into the first aperture 200 a, and thefirst and second electrodes 510, 512 extend through the first aperture200 a and outward from the bottom of the body 102. In other examples,the connectors 202 a, 506 may be other types of connectors. Thesemagnetic couplings (or other releasable mechanical couplings) allow theelectrode units 500 to be independently coupled to the headset 100. Assuch, the independently couplable electrode units 500 can be repaired orreplaced individually, which extends the useful life of the headset 100by enabling replacement of individual electrode units 500 instead of theentire headset 100.

The first and second electrodes 510, 512 sense EEG signals from thescalp of a subject. The signals are transferred from the pins 1002through the electrode bodies 1000, the spring 504, and the connector 506to the first connector 202 a. As described above, a PCB may be disposedwithin the body 102 to electrically couple the first connector 202 a tothe processor 434 (FIG. 4C) and/or a transmitter. In some examples, thefirst and second electrodes 510, 512 and the spring 504 are electricallyconductive, whereas the guide 508 and the housing 514 are notelectrically conductive. For example the first and second electrodes510, 512 and the spring 504 may be metallic (e.g., steel, silver,silver-chloride, chromium, gold, etc.) and the guide 508 and the housing514 may be plastic or rubber and/or other suitable material(s) orcombination of material(s).

In the illustrated example, the electrode unit 500 includes twoelectrodes. However, in other examples, the electrode unit 500 mayinclude more or fewer electrodes and/or pins. For example, the electrodeunit 500 may include only one electrode. In another example, theelectrode unit 500 may include three electrodes, four electrodes, tenelectrodes, etc.

FIG. 12 shows the spring 504, the connector 506, the guide 508 and thefirst and second electrodes 510, 512 of the electrode unit 500 (FIG. 5)in the extended position, similar to FIGS. 8 and 10. In FIG. 12, thepusher 502 and the housing 514 have been removed for clarity. In theillustrated example, the spring 504 is relaxed or in an unbiased state.FIG. 13 shows the spring 504 in a biased state, similar to FIG. 11. Thefirst and second electrodes 510, 512 (FIG. 12) are pushed upward throughthe guide 508 and onto the bottom of the spring 504. As a result, amiddle of the spring 504 flexes upward. In the biased state, the spring504 biases the first and second electrodes 510, 512 downward.

FIG. 14 is a cross-sectional view of the spring 504, the connector 506,the guide 508 and the first and second electrodes 510, 512 taken alongline C-C of FIG. 12, showing the first and second electrodes 510, 512 inthe extended position, similar to FIG. 10. FIG. 15 is a cross-sectionalview of the spring 504, the connector 506, the guide 508 and the firstand second electrodes 510, 512 taken along line D-D of FIG. 13, showingthe first and second electrodes in the retracted position, similar toFIG. 11.

FIGS. 16-18 illustrate another example electrode unit 1600 that may beused with the example headset 100 of FIGS. 1-4E. In FIGS. 16-18, theelectrode unit 1600 is illustrated as coupled to the head band 104 ofthe headset 100 (FIG. 1). In the illustrated example, the electrode unit1600 includes an electrode 1602, a housing 1604, a connector 1606 andinsulation 1608. As illustrated in FIG. 18, the electrode 1602 includesan electrode body 1610 (e.g., a housing, a sheath) and a pin 1612 (e.g.,a pogo pin). The electrode body 1610 receives the pin 1612 within acavity 1614 of the electrode body 1610. The pin 1612 of the illustratedexample is retractable into the cavity 1614 and biased outward from theelectrode body 1610 by a spring 1616 that is disposed within the cavity1614. A tip 1618 of the pin 1612 contacts the scalp of the head of asubject and senses the EEG signals.

In the illustrated example of FIGS. 16-18, the insulation 1608 and theelectrode body 1610 are disposed within a cavity 1620 of the housing1604. The insulation 1608 is located between the electrode body 1610 andan inner wall 1622 of the cavity 1620. In some examples, the cavity 1620is implemented as a blind hole.

As discussed above, the bands 104, 106, 108, 110, 112 of the headset 100include the plurality of apertures 200 a-200 n extending through thebands 104, 106, 108, 110, 112, and the plurality of connectors 202 a-202n are disposed around the apertures 200 a-200 n. In FIGS. 16-18, theelectrode unit 1600 is illustrated as coupled to the first aperture 200a. The electrode 1602 extends through the first aperture 200 a. In theillustrated example, the connector 1606 is a magnet, and the firstconnector 202 a is a metal ring. As such, the electrode unit 1600 ismagnetically coupled to the head band 104, and, thus, releasably coupledthereto. In the illustrated example, the connector 1606 is disposedbetween a flange 1623 extending from the electrode body 1610 and theinsulation 1608. When the electrode unit 1600 is disposed on the headband 104, the attractive force between the connector 1606 and the firstconnector 202 a retains in the electrode unit 1600 on the head band 104.In other examples, the connector 1606 and the first connector 202 a maybe other types of connectors to removably couple the electrode unit 1600to the head band 104.

As illustrated in FIGS. 16 and 18, a PCB 1624 is disposed within (e.g.,entirely encased in) the head band 104. The PCB 1624 communicativelycouples the first connector 202 a to the electrical connector 300 (FIG.4C). Signals gathered by the electrode 1602 are transferred from theelectrode pin 1612, through the electrode body 1610 and the flange 1623,to the first connector 202 a, to the PCB 1624 and, thus, to theelectrical connector 300. Because the PCB 1624 acts primarily as aconductor and need not include logic circuitry, in some examples the PCB1624 is replaced with other conductors such as wires.

In some examples, shielding is desired to block or prevent noise orother signals (e.g., interference) from adversely affecting the EEGsignals gathered by the electrode 1602. In the illustrated example, thehead band 104 includes an electrical pin 1626 adjacent the firstaperture 200 a. When the electrode unit 1600 is coupled to the firstaperture 200 a, the electrical pin 1626 contacts a bottom 1628 of thehousing 1604. A layer of conductive paint or paste 1630 is disposed onthe bottom 1628 of the housing and along the inner wall 1622 of thecavity 1620. The electrical pin 1626 is coupled (e.g., soldered) to thePCB 1624. In some examples, a wire or trace in the PCB 1624 electricallycouples the pin 1626 to a shielding electrode, which may be in contactwith the head (e.g., forehead) of the subject. Thus, the paste 1630 isin electrical connection with the body of the wearer, which acts as anextension of the body that surrounds the electrode 1602, therebyshielding the electrode 1602 from any interference or noise in theenvironment. For example, referring back to FIG. 2, the example headset100 includes six flat electrodes 204 a, 204 b, 204 c, 204 d, 204 e, 204f coupled to the head band 104 (e.g., molded in the body 102 of the headband 104) and disposed along the forehead side of the head band 104. Theflat electrodes 204 a-204 f are communicatively coupled to the PCB 1624in the body 102 of the headset 100 and/or to other wires or tracesdisposed in the body 102 of the headset 100. In some examples, one ofthe flat electrodes 204 a-204 f is a shielding electrode, which iscommunicatively coupled to the pin 1626 (and other pins associated withthe other apertures 200 a-200 n). In some examples, three of the flatelectrodes 204 a-204 f are to gather EEG signals, one of the flatelectrodes 204 a-204 f is a ground electrode, one of the flat electrodes204 a-204 f is a reference or feed-back electrode and one of the flatelectrodes 204 a-204 f is a shielding electrode. In other examples, oneor more of the flat electrodes 204 a-204 f may have different functions.In some examples, more or fewer flat electrodes are implemented.

In some examples, a shield layer (e.g., a layer of silver or copper) isdisposed on top of the PCB 1624 (or molded into the body 102 of theheadset 100 over the PCB 1624) and integrated throughout the body 102 ofthe headset 100. The shield layer is also electrically coupled to theshielding electrode on the forehead of the subject and, thus, shieldsthe PCB 1624 in a similar manner. In some examples, the shield layer iselectrically coupled to a shield layer in the processor 434 (which isdisposed over the electrical components in the processor 434) tolikewise shield any electrical components in the processor 434. Thus, apassive shield can be formed around the electrical components of theheadset 100. In other examples, a charge may be provided to the pin 1626and are distributed throughout the paste 1630 to block noise andinterference. In some examples, a metallic mesh or pattern (e.g., acage) is disposed around the electrode 1602. In some examples, theelectrical pin 1626 is biased upward from the head band 104 (e.g., via aspring, similar to the first spring 1006 and the first pin 1002 in FIG.10) such that the electrical pin 1626 retracts into a base or body whencontacted by the housing 1604. In other examples, the electrical pin1626 is integrated with the electrode unit 1600 and contacts a pad nearthe first aperture 200 a when connected to the headset 100 (disclosed infurther detail here).

In FIGS. 16-18, the electrode unit 1600 is illustrated as coupled to thehead band 104. However, in other examples, the electrode unit 1600 maybe similarly coupled to other ones of the bands (e.g., the first band106, the second band 108, the third band 110, or the midline band 112).In some examples, multiples electrode units similar (e.g., identical) tothe electrode unit 1600 are coupled to the headset 100 (FIGS. 1-4E).

FIGS. 19, 20 and 21 illustrate another example electrode unit 1900 thatmay be used with the example headset 100 of FIGS. 1-4E. In theillustrated example, the electrode unit 1900 includes an electrode 1902,a housing 1904 and a connector 1906. In FIGS. 19 and 20, the interiorstructure of the housing 1904 is shown in dashed lines. The electrode1902 includes an arm 1908 and a ring 1910. In the illustrated example,the housing 1904 includes a cavity 1912. The ring 1910 of the electrode1902 is disposed around an opening 1914 of the cavity 1912. In theillustrated example, the ring 1910 is coupled between the connector 1906and a bottom 1916 of the housing 1904. The arm 1908 is bent or curved inthis example. A first end of the arm 1908 is coupled to the ring 1910,and the other end of the arm 1908 extends through an opening 1918 of thering 1910 and into the cavity 1912 of the housing 1904 (see also FIG.25).

The example electrode unit 1900 may be coupled to one of the apertures200 a-200 n of the headset 100 of FIGS. 1-4. In some examples, theconnector 1906 is a magnet, and the connectors 202 a-202 n (FIG. 3) aremetal rings. As such, the connector 1906 magnetically couples theelectrode unit 1900 to one of the connectors 202 a-202 n. When coupledto one of the connectors 202 a-202 n, the arm 1908 of the electrode 1902extends through the respective aperture 200 a-200 n to contact the scalpof a subject when the headset 100 is disposed on the head of thesubject. In FIGS. 19-21, the example electrode 1902 is in anuncompressed state. Signals gathered by the electrode 1902 aretransferred through the connector 1906 to the connector 202 a-202 n andto the electrical connector 300 (FIG. 3) via the PCB (or otherconnective wiring) disposed within the body 102 of the headset 100.

FIGS. 22-24 illustrate the example electrode 1902 in an unassembled(e.g., unshaped or unbent) state or form. The electrode 1902 may bestamped or cut from a substrate such as, for example, a sheet of silver,silver-chloride, chromium, gold, and/or any other suitable metal(s),alloy(s) or other conductive material(s) or combination thereof. In theillustrated example, the electrode 1902 includes the ring 1910 and thearm 1908 extending from the ring 1910. FIGS. 25-27 illustrate theelectrode 1902 in an assembled state or form. To form the electrode 1902from the unassembled electrode 1902 of FIG. 22, the arm 1908 is bentover the ring 1910, inserted through the opening 1918 and creased orbent, such that a portion of the arm 1908 extends back through theopening 1918. For example, as illustrated in FIGS. 25-27, a firstportion 2500 of the arm 1908 extends downward from the ring 1910(through the opening 1918) and, at a corner or bend 2502, a secondportion 2504 of the arm 1908 extends back upward through the opening1918 of the ring 1910. The first and second portions 2500, 2504 arecoupled at the bend 2502. In some examples, the first and secondportions 2500, 2504 are integral. The electrode 1902 as illustrated inFIG. 25 may be formed by bending the arm 1908 over the ring 1910 andthrough the opening 1918. In other examples, the arm 1908 may be bentdownward on the outside of the circumference of the ring 1910, bent orcreased to form the corner or bend 2502 and positioned back through theopening 1918 of the ring 1910. Other examples include a curve in placeof the bend 2502, which may be used, for example, to increase thesurface area of the connection of the electrode 1902 on the scalp and/orprovide increased comfort to the subject.

FIGS. 28-30 illustrate the example housing 1904 of the electrode unit1900 (FIG. 19). In particular, FIG. 28 is a side view of the housing1904, FIG. 29 is a bottom view of the housing 1904 and FIG. 30 is across-sectional view of the housing 1904 taken along line G-G of FIG.28. As illustrated in FIGS. 29 and 30, the cavity 1912 extends into thehousing 1904 from the opening 1914 in the bottom 1916. In theillustrated example, a first groove or recess 2900 is formed around theopening 1914. The first recess 2900 is sized to receive the connector1906 (FIG. 19). A second groove or recess 2902 is formed above the firstrecess 2900 and is sized to receive the ring 1910 (FIG. 19) of theelectrode 1902. In some examples, the connector 1906 is retained in thefirst recess 2900 via an interference fit (e.g., friction fit). In otherexamples, chemical, magnetic, and/or mechanical fasteners may be used tocouple to the connector 1906 to the housing 1904.

In the illustrated example, the cavity 1912 includes a first channel2904 (e.g., a slot) and a second channel 2906 extending into the housing1904. When the arm 1908 of the electrode is compressed, the secondportion 2504 (FIG. 25) of the arm 1908 is disposed within one of thefirst channel 2904 or the second channel 2906 (as discussed in furtherdetail herein). As such, the electrode 1902 can be oriented in one oftwo orientations (e.g., with the second portion 2504 extending into thefirst channel 2904 or the second channel 2906). In other examples, thecavity 1912 may include only one channel. In other examples, the cavity1912 may include more than two channels, or may include a continuouschannel such that electrode 1902 can be positioned in the housing 1904in any orientation.

In the illustrated example of FIGS. 29 and 30, a guide 2908 is disposedwithin the cavity 1912. The guide 2908 is a cylinder that extends froman inner wall of the cavity 1912 and is sized to receive the ring 1910of the electrode 1902 and align the electrode 1902 within the opening1914 of the housing 1904. As illustrated in FIG. 29, the guide 2908includes a first slot 2910 that is aligned with the first channel 2904of the cavity 1912 and a second slot 2912 that is aligned with thesecond channel 2906 of the cavity 1912. As a result, the arm 1908 of theelectrode 1902 can extend through one of the first or second slots 2910,2912 and into the respective first or second channel 2904, 2906 of thecavity 1912.

FIGS. 31-33 illustrate the example electrode 1902 of the electrode unit1900 in a bent or compressed state, such as when the electrode 1902 isin contact with the scalp of a subject. In FIGS. 31 and 32, the interiorstructure of the housing 1904 is shown in dashed lines. For example,when the electrode unit 1900 is attached to a headset (e.g., the headset100 of FIGS. 1-4), the electrode 1902 extends through an aperture in theheadset to contact the head of a subject. In particular, the bend 2502contacts the head of the subject. The arm 1908 bends or compresses toreduce or soften the contact between the bend 2502 and the scalp of thesubject. In other words, the electrode 1902 acts as a spring to biasesthe bend 2502 downward from the opening 1914. The electrode 1902 has asimilar mechanical movement as a leaf spring. As illustrated in FIGS.31-33, when a force is applied to the bend 2502 (e.g., resistance fromthe scalp of the subject when the headset 100 is tightened), the firstportion 2500 and the second portion 2504 of the arm 1908 bend or curve.In some examples, the first portion 2500 moves toward the second portion2504 when force is applied to the bend 2502. As the bend 2502 is movedupward toward the opening 1914, the second portion 2504 of the arm 1908slides into the first channel 2904 of the cavity 1912. Referring back toFIGS. 22, 23, and 25, the ring 1910 includes a notch 2506 formed in therim of the opening 1918. In some examples, when the arm 1908 iscompressed, as illustrated in FIGS. 31-33, the second portion 2504 ismoved into the notch 2506, and the notch 2506 functions as a guide. EEGsignals are transferred from the bend 2502, through the first portion2500 (or the second portion 2504) to the ring 1910, to the connector1906, and from the connector 1906 to one of the connectors 202 a-202 n(FIG. 3) of the headset 100. The signals are then transferred from theone of the connectors 202 a-202 n to the electrical connector 300 (FIG.4A) via the PCB.

As disclosed herein, the electrode 1902 may be stamped or cut from asubstrate such as, for example, the substrates disclose above. FIG. 34illustrates example electrodes 1902 a-1904 d stamped into a substrate3400. The substrate 3400 may include steel, silver, silver-chloride,chromium, gold and/or any other suitable material or combination ofmaterial(s). As such, multiple electrodes can be manufactured relativelyquickly and for low cost.

FIGS. 35-39 illustrate another example electrode unit 3500 that may beused with the example headset 100 of FIGS. 1-4E. As illustrated in theexploded view of FIG. 35, the electrode unit 3500 includes a housing3502, a spring 3504, a support 3506, a first electrode 3508, a secondelectrode 3510, a guide 3512 and a connector 3514. In the illustratedexample, the first and second electrodes 3508, 3510 are substantiallythe same as the first and second electrodes 510, 512 of the electrodeunit 500 (FIG. 5) and include pins (e.g., pogo pins) that are biasedoutward. In the illustrated example, the first and second electrodes3508, 3510 are coupled to the spring 3504 via the support 3506. In someexamples, the support 3506 includes one or more tabs or protrusions thatextend through openings in the spring 3504 and which may be staked orpress fit (similar to the first and second electrodes 510, 512). Inother examples, the support 3506 is coupled to the spring 3504 via othermechanical and/or chemical fasteners.

The first and second electrodes 3508, 3510 are slidably disposed withinan opening 3516 of the guide 3512, and the guide 3512 is dimensioned tobe disposed within an opening 3518 of the connector 3514. In someexamples, the guide 3512 is coupled to the connector 3514 via aninterference fit (e.g., friction or press fit). Additionally oralternatively, in some examples a chemical fastener such as an adhesiveand/or a mechanical fastener(s) may be used to couple the guide 3512 tothe connector 3514. The connector 3514 is dimensioned to be insertedinto an opening 3520 in the housing 3502. In some examples, theconnector 3514 is coupled to the housing 3502 via an interference fit(e.g., friction or press fit). Additionally or alternatively, in someexamples a chemical fastener such as an adhesive and/or a mechanicalfastener(s) may be used to couple the connector 3514 to the housing3502. When the connector 3514 is inserted into the opening 3520 of thehousing 3502, the spring 3504 is clamped between the connector 3514 anda ledge 3522 in the opening 3520 of the housing 3502. The connector 3514couples the electrode unit 3500 to one of the connectors 202 a-202 n ofthe example headset 100 in FIGS. 1-4E, similar to the other electrodeunits disclosed herein. When the electrode unit 3500 is assembled, thespring 3504 is disposed over the opening 3516 of the guide 3512. Similarto the electrode unit 500 (FIG. 5) disclosed above, the spring 3504increases the comfort and wearability of the headset 100 by reducing thepressure the first and second electrodes 3508, 3510 apply to the scalp.As the first and second electrodes 3508, 3510 are pushed upwards, thecenter section of the spring 3504 flexes upward into the opening 3520 ofthe housing 3502. Electrical signals from the first and secondelectrodes 3508, 3510 are transmitted through the support 3506 to thespring 3504, and through the spring 3504 to the connector 3514, which isin contact with one of the connectors 202 a-202 n of the headset 100(FIGS. 1-4E).

FIG. 36 illustrates an assembled view of the example electrode unit3500, FIG. 37 illustrates a side view of the example electrode unit3500, FIG. 38 illustrates another side view of the example electrodeunit 3500, and FIG. 39 illustrates a cross-sectional view of the exampleelectrode unit 3500 taken along line I-I of FIG. 38. As illustrated inFIGS. 36-39, when the connector 3514 is received within the housing3502, the connector 3514 is substantially flush or even with a bottom3524 of the housing 3502 and the guide 3512 and the first and secondelectrodes 3508, 3510 extend from the bottom 3524 of the housing 35012.When the first and second electrodes 3508, 3510 contact the scalp, thepins of the first and second electrodes 3508, 3510 retract and/or thefirst and second electrodes 3508, 3510 retract into the opening 3520 ofthe housing 3502 as disclosed in other examples herein. As illustratedin FIG. 39, the outer rim/perimeter of the spring 3504 is coupled (e.g.,retained) between ledge 3522 of the housing 3502 and the connector 3514,which is coupled to the housing 3502.

In some examples, shielding may be desired for the electrode unit 3500.FIG. 40 illustrates an example shielding unit 4000 that may beimplemented to shield the example electrode unit 3500. In theillustrated example, the shielding unit 4000 includes a top cover 4002(e.g., a first cover) and a bottom cover 4004 (e.g., a second cover).The bottom cover 4004 includes an opening 4006 to receive the electrodeunit 3500. The opening 4006 extends from a top side 4007 to a bottomside 4009 of the bottom cover 4004. When the electrode unit 3500 isdisposed in the bottom cover 4004, the first and second electrodes 3508,3510 extend from the bottom, such that the first and second electrodes3508, 3510 can extend through one of the apertures 200 a-200 n of theexample headset 100 (FIGS. 1-4E). For example, in the illustratedexample, the shielding unit 4000 (with the electrode unit 3500 disposedtherein) may be coupled to the first aperture 200 a on the head band104. The connector 3514 couples (e.g., magnetically) the electrode unit3500 (and, thus, the shielding unit 4000) to the connector 202 a. Thetop cover 4002 is coupled to the top side 4007 of the bottom cover 4004.

In some examples, to retain the electrode unit 3500 in the bottom cover4004, the housing 3502 is coupled to the bottom cover 4004 via aninterference fit (e.g., friction or press fit). Additionally oralternatively, in some examples a chemical fastener such as an adhesiveand/or a mechanical fastener(s) may be used to couple the housing 3502to the bottom cover 4004. In the illustrated example, the shielding unit4000 includes a pin 4008 that is disposed within a channel 4010extending through the bottom cover 4004. The pin 4008 extends from thebottom cover 4004 and, when the shielding unit 4000 is coupled to one ofthe apertures 200 a-200 j of the headset 100, the pin 4008 contacts anelectrical pad 4012 (e.g., a metal pad) adjacent the first aperture 200a. The other end of the pin 4008 contacts a layer of conductive paste4014 that is distributed around a bottom 4016 of the top cover 4002,similar to the layer of conductive paste 1630 on the bottom 1628 of thehousing 1604 in FIG. 18. In some examples, the pin 4008 is a pogo-pin(e.g., similar to the pogo-pin electrode in FIG. 41). The electrical pad4012 is electrically coupled, via the PCB 1624 and/or other traces orwires, to a shield electrode (e.g., one of the flat electrodes 204 a-204f (FIG. 2) the forehead), similar to the example electrode unit 1600 inFIGS. 16-19. In the illustrated example, the pin 4008 is a spring-loadedpin (e.g., a pogo-pin), similar to the pin 1626 of FIGS. 16-18. In otherexamples, the pin 4008 is not spring-loaded. While the example shieldingunit 4000 is described in connection with the example electrode unit3500, it is understood that any other electrode unit such as the exampleelectrode units 500, 1600, 1900 may be similarly contained in theshielding unit 4000. As such, the example shielding unit 4000 can beemployed to provide shielding to other electrode units.

FIG. 41 illustrates a cross-sectional view an example pogo-pin electrode4100. Any of the example electrodes disclosed herein (e.g., theelectrodes 510, 512, 1602, 3508, 3510) may be implemented as the exampleelectrode 4100. The electrode 4100 includes a body 4102 and a pin 4104that is retractable into an opening 4106 in the body 4102. A spring 4108is disposed in the opening 4106 and biases the pin 4104 outward. To keepthe pin 4104 from being ejected from the opening 4106, an edge 4110 ofthe body 4102 around the opening 4106 is angled inwards. Additionally,an upper section 4112 of the pin 4104 is widen. The upper section 4112of the pin 4104 engages the edge 4110 of the body 4102, which preventsthe pin 4104 from being ejected. In some examples, one or more groundelectrodes are implemented in gathering the EEG signals. A groundelectrode may be coupled to another part of the subject's body, such asthe ear, the finger, the forehead (e.g., one of the flat electrodes 204a-204 f of FIG. 2), behind the mastoid, etc. The ground electrode(s) areelectrically coupled to a signal acquisition unit (e.g., the processor434 of FIG. 4C). In some examples, one or more body-sense electrodes(e.g., a control electrode, a reference electrode, a feed-backelectrode) are used to enhance the signal acquisition process. Thebody-sense electrode(s) are coupled to the ear lobe, the nose, and/orany other area on the body having sufficient connectivity and lowexposure to brain and/other body signals. The body sense electrode maybe one of the flat electrodes 204 a-204 f of FIG. 2, for example. Thebody sense electrode(s) measure or obtain signals generated by noise andinterference in the environment. The noise or interference signals canbe subtracted from the desired signals obtained by the electrodes on theheadset, thereby offsetting any noise or interface signals picked up bythe headset electrodes. In some examples, the signals provided by thebody-sense electrodes are inverted and fed into the ground signal,(e.g., to create a driven voltage). In some examples, one or more of thedisclosed electrode units are implemented as a ground electrode and/orbody-sense electrode.

From the foregoing, it will be appreciated that electrode units havebeen disclosed that can removably couple to a headset, such as theheadset 100 of FIGS. 1-4E. In some examples, the electrode units can beindependently removed from the headset to be cleaned, repaired and/orreplaced, for example. Additionally, because the electrode units are notfixedly attached to the headset, the electrode units can be easilyremoved if caught or snagged on a foreign object (e.g., hair), therebyreducing the risk of injury to the subject or damage to the headset.Further, some example electrodes disclosed herein are manufactured bystamping the electrodes from a substrate, such as, for example metals oralloys. Therefore, the electrodes can be manufactured relatively quicklyand for low cost.

Although certain example apparatus have been described herein, the scopeof coverage of this patent is not limited thereto. On the contrary, thispatent covers all methods, apparatus, and articles of manufacture fairlyfalling within the scope of the appended claims either literally orunder the doctrine of equivalents.

What is claimed is:
 1. An electrode unit comprising: a guide having afirst opening; an electrode disposed in the first opening, the electrodemovable in the first opening, the electrode having a body, a firstspring, and a pin, the pin biased outward from a first end of the bodyvia the first spring; a second spring disposed over the first openingand engaged with a second end of the body; a connector having a secondopening, the guide disposed in the second opening, the connector toremovably couple the electrode unit to a band to be disposed over a headof a subject, the connector being electrically conductive, the secondspring in contact with the connector such that an electrical signalobtained by the electrode is transferred through the second spring andthrough the connector to the band; and an electrode unit housing havinga third opening, the connector disposed in the third opening.
 2. Theelectrode unit of claim 1, wherein the electrode is a first electrode,the body is a first body, the pin is a first pin, and further includinga second electrode disposed in the first opening.
 3. The electrode unitof claim 2, wherein the second electrode includes a second body, a thirdspring, and a second pin, the second pin biased outward from a first endof the second body via the third spring.
 4. The electrode unit of claim3, wherein the first electrode and the second electrode areindependently adjustable via the first spring and the third spring. 5.The electrode unit of claim 4, wherein the first electrode and thesecond electrode are simultaneously adjustable via the second spring. 6.The electrode unit of claim 1, wherein the body is coupled to the secondspring.
 7. The electrode unit of claim 6, wherein the body includes aprotrusion extending through an aperture in the second spring, the bodycoupled to the second spring via a staking or press fit connection. 8.The electrode unit of claim 1, wherein the connector is a magnet.
 9. Theelectrode unit of claim 1, wherein the guide is coupled to the connectorvia an interference fit.
 10. The electrode unit of claim 1, wherein theconnector is substantially aligned with a bottom of the electrode unithousing, the guide and the electrode extending from the bottom of theelectrode unit housing.
 11. The electrode unit of claim 1, wherein theelectrode is movable through the first opening of the guide into acavity of the electrode unit housing.
 12. The electrode unit of claim11, wherein the second spring is disposed over the connector and theguide in the cavity.
 13. The electrode unit of claim 12, wherein, whenthe electrode moves into the cavity of the electrode unit housing, acenter of the second spring flexes into the cavity.
 14. The electrodeunit of claim 13, further including a pusher disposed in the cavity, anouter rim of the second spring coupled between the pusher and theconnector.
 15. The electrode unit of claim 14, wherein the pusher isinserted into the cavity from a fourth opening in the electrode unithousing opposite the third opening.
 16. The electrode unit of claim 13,wherein the electrode unit housing includes a ledge in the thirdopening, wherein an outer rim of the second spring is coupled betweenthe connector and the ledge.
 17. The electrode unit of claim 13, whereinan outer rim of the second spring remains in contact with the connectorwhen the center of the second spring flexes into the cavity.
 18. Theelectrode unit of claim 1, wherein the second spring is a spiral springplate.
 19. An electrode unit comprising: a connector having an opening;a guide disposed in the opening of the connector, the guide having afirst end, a second end opposite the first end, and a passage extendingbetween a first opening in the first end and a second opening in thesecond end; an electrode movably disposed in the passage, the electrodehaving a body, a first spring, and a pin, the pin biased outward from anend of the body via the first spring; and a spiral spring plate disposedover the opening of the connector and the first opening of the guide, anouter rim of the spiral spring plate in contact with the connector, thebody of the electrode engaged with the spiral spring plate such that thespiral spring plate biases the electrode outward from the second openingin the second end of the guide, the spiral spring plate movable betweenan unbiased state in which the second spring is substantially flat and abiased state in which a center of the spiral spring plate flexes awayfrom the guide and the connector while the outer rim of the spiralspring plate remains in contact with the connector.
 20. The electrodeunit of claim 19, wherein the electrode is a first electrode, furtherincluding a second electrode movably disposed in the passage.
 21. Theelectrode unit of claim 1, wherein the guide and the electrode unithousing are not electrically conductive.